    Patent Document 1: Japanese Patent Laying-Open No. 04-074766    Patent Document 2: Japanese Patent Laying-Open No. 04-114966    Non-Patent Document 1: F. P. Bundy, J. Chem. Phys., 38 (1963) pp. 631-643    Non-Patent Document 2: M. Wakatsuki et al., Japan. J. Appl. Phys., 11 (1972) pp. 578-590    Non-Patent Document 3: S. Naka et al., Nature, 259 (1976) p. 38
In a diamond polycrystalline body conventionally used in a cutting tool, a tool such as a dresser or a die, a drill bit, or the like, an iron group metal such as Co, Ni or Fe or ceramic such as SiC is used as a sintering aid or a binder. Use of a carbonate as a sintering aid is also known ([Patent Document 1], [Patent Document 2]). The diamond polycrystalline body as such is obtained by sintering diamond powder together with the sintering aid or binder in a high pressure and temperature condition (generally a pressure of 5-8 GPa and a temperature of 1,300-2,200° C.), in which condition diamond is thermodynamically stable. A naturally occurring diamond polycrystalline body (carbonado or ballas) is also known and is partially used as a drill bit, but is not generally used in industry because of large variations in a material and a small amount of output thereof.